No other way to tell Lee. The G80 Eaton Locking Diff aka Gov-Lok also spins the wheels in opposite direction like as if it were an open diff, instead of both wheels in the same direction like MOST lockers or limited slips. One way to know, would be to jack up one rear wheel on a floor jack. Then get in your truck, put it in gear and see if you can drive it on the floor jack about 4-6 feet up your driveway. If you can, then you likely have the G80. If not, and the wheel in the air just spins, then you most likely have an open diff or a G80 that is broken. I myself, would prefer not to have a G80. If you have an open diff, you can install a Lock Right Locker. The Lock Rights are not the strongest systems though. They can handle up to 350hp and max of 35in tire. If I was running 33in tire and 300hp, I'd feel better about the Lock Right.
Its an inexpensive system in comparison to other lockers, and it easy to install. If you have the full float rear end, you don't even have to jack it up or remove your tires to install the Lock Right. Just take off your axle bolts, slide the axles out about 6 inches on each axle. Take the rear cover off, remove the spider gears, put the Lock Right unit in the carrier in place of the spider gears. Cover back on, fill with gear oil, slide axles back in and done. Go raise hell !!! JMO
Or you could spend the big bucks and go with a Detroit Locker.